The 67mm ND8 QuartzLine Solid Neutral Density 0.9 and Circular Polarizer Filter from PolarPro is a filter that combines a solid neutral density effect with a circular polarizer effect. When in use, this filter's 8x filter factor provides a 3-stop exposure reduction. Its 0.9 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily.Simultaneously, this filter can help to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface. The light from the sun naturally becomes partially polarized due to reflecting off electrons in air molecules, causing the light to scatter into what appears as haze. A polarizing filter arranges and filters this directionally polarized light perpendicularly to the reflected light, allowing for the absorption of much of this light. This results in a noticeable reduction of glare and reflections from non-metallic surfaces and an increase in the saturation of skies and foliage.A circular polarizer only differs from a linear polarizer in that it contains a quarter wave plane in addition to the linear polarizing filter. The addition of this quarter wave plane is to circularly polarize the linearly polarized light for the use of auto focus and exposure functions. Due to how the light is broken down and filtered with a linear polarizer, auto focus and exposure accuracy become skewed during use. When the light becomes circularly polarized, it permits the use of these functions.This filter is constructed from quartz glass for enhanced durability. To prevent internal ghosting and reflections, 16 layers of anti-reflection coatings offer scratch protection to the filter substrate while promoting clarity and color fidelity. The coatings associated with the PolarPro 67mm ND8 QuartzLine Solid Neutral Density 0.9 and Circular Polarizer Filter also result in an improved beading effect when in contact with water or oil, allowing for more efficient cleaning.The quartz glass is set within a brass filter ring with side knurlings that can be rotated in order to adjust the intensity of the polarization effect. Together, the brass material and knurlings prevent jamming and provide additional strength, as well as a textured grip when mounting or removing this filter from a lens.0.9 neutral density filter effect darkens the image, allowing you to photograph with a longer shutter speed or wider aperture than normally requiredProviding an 8x filter factor with a 3-stop exposure reduction, this filter allows you to control depth of field and convey movement more easilyPolarizing filter effect arranges and filters directionally polarized light perpendicularly to the reflected light, allowing for the absorption of much of the lightHelps to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surfaceClears up haze in distant landscapes and provides more saturated, vivid colorsStrongest polarization effect when used at a 90° angle from the sunCircular polarizer effect is ideal for use with digital cameras and autofocus lenses, where a linear polarizer will often disrupt auto exposure and focus featuresConstructed from quartz glass for enhanced durabilityMulti-coated to prevent internal ghosting and reflections while promoting clarity as well as color fidelityBrass filter ring helps to prevent jamming and provides additional strengthFilter ring can be rotated to adjust the intensity of the polarization effect67mm front filter threads allow for use with other filtersSide knurlings provide a textured grip when mounting or removing from a lensPlastic filter case and padded pouch for storage and transportMicrofiber cloth for cleaning and maintenance